title: A 2D homochiral inorganic-organic framework exhibiting a spin-flop transition.
abstract: A 2D homochiral inorganic-organic framework {[Mn(NPTA)(4,4'-bpy)(H(2)O)]·(H(2)O)(2)}(n) was prepared by assembling achiral polar 4-nitrophthalic acid, manganese ions, and ancillary 4,4'-bipyridine ligands (NPTA = 4-nitrophthalate) (4,4'-bpy = 4,4'-bipyridine). The isomorphous Zn(ii) compound was also prepared as a diamagnetic analogue. Adjacent manganese spin centres are linked by the syn-anti carboxylate to form a helical chain, and chains of the same chirality are connected by 4,4'-bpy ligands to generate a homochiral layered framework. Edge-to-face aromatic interactions between neighboring layers lead to a 3D homochiral supramolecular structure. Magnetization and heat capacity measurements indicate that the framework is a weak antiferromagnet at low applied field. The magnetic interactions between adjacent manganese ions in the helical chain can be fitted using the 1D Fisher model, with 2J/k = -0.68 K and g = 2.00. Moreover, the compound displays a unique field-dependent spin-flop transition in high magnetic fields, with a critical field of 23.6 kOe at 1.9 K.
authors.affiliation: University of Cambridge, Department of Materials Science and Metallurgy, Pembroke Street, Cambridge, UK CB2 3QZ.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Phillip T
authors.initials: PT
authors.lastname: Barton
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Burwood
authors.forename: Anthony K
authors.initials: AK
authors.lastname: Cheetham